1. Field of the Invention
This invention relates to a hand pump for dispensing creamy or liquid substances, including atomized dispensing, at a predetermined constant pressure, the pump having no metal parts in contact with the substance to be dispensed.
2. Discussion of the Related Art
Numerous types of manually operated pumps exist which when operated dispense creamy or liquid substances in atomized form.
These pumps generally suffer from the drawback that as the dispensed liquid or fluid passes through the pump ducts it comes into contact with metal components such as springs or balls, which limits their use to non-corrosive fluids and liquids, or to fluids and liquids which cannot be contaminated by said metal components. In addition, the more simple types of such pumps also suffer from the drawback that the quality of atomization of the dispensed liquid and the pressure with which it leaves the nozzle of the dispenser applied to the pump depend on the speed with which the pump is operated and the force applied.
Pumps of known type are constructed such that the creamy or liquid substance is dispensed only when it has reached a certain pressure within the pressure chamber. These pumps generally comprise a valving member movable against a spring, which closes the passage for the creamy or liquid substance through the duct leading to the dispensing nozzle. This passage opens only when a certain pressure has been transmitted to the creamy or liquid substance contained in the pressure chamber. Under rest conditions, the valving member seals against an abutment rigid with a movable stem forming part of the pump. When the opposing force of the spring has been overcome, the valving member opens to provide the creamy or liquid substance with only a very narrow passage for its delivery, this generating a large pressure drop which allows only a weak flow, with the result that the creamy or liquid substance leaves the nozzle dripping and poorly atomized.
A defect of these pumps is therefore the fact that as the valving member opens gradually and slowly it does not allow effective atomization during opening and closure, resulting in dripping. In addition, in said pumps of known type the creamy of liquid substance is in contact with the metal parts of the pump.